3 Ways to Clean Aircon
1. General servicing
This is the cheapest but most ineffective way. One fancoil costs between $35-$50, the servicing company will usually give some discount if you clean more units. The problem with this method is the technician will simply remove the outermost cover and filter and use a vacuum cleaner to try to suck out the dirt, but it's really very ineffective, I would say they can only clean out at the most 5% of the dirt in your unit, or worse, not even 1%. If you don't believe me, after they clean it, you try opening up the unit and see for yourself, it will still be full of dirt and mold, and if you put your nose close to the area where the air comes out, you will smell something like dirty socks. And the worst part is aircon servicing companies will usually suggest you to at least do this cleaning once every 3 months, just imagine how much money you will be wasting, you might as well open it up and vacuum by yourself, it doesn't take more than 10 minutes to clean one unit, and the cover is not that difficult to open, not the mention the filter, I'm serious.
2. Chemical spray
I think this costs anywhere less than $100. For this way, they are using some sort of spray jet to clean the evaporator, I think this is fairly effective, it does clean out most of the dirt that can be seen by eyes but the problem is, it cannot clean blind spots, but it's still better than the useless general servicing, if you are on budget and still need to clean your unit, this is the way to go.
3. Chemical overhaul
This is the most effective, it costs between $150-$160, I see some companies offering $120, I would stick to the more reliable ones, money should not be an issue here, it's the ultimate cleaning, if you want to spend, might as well make sure you are getting the right people to do it. Anyway you are not going to do this very often, probably once in a year or maybe even two years. The reason why this is the most effective is they dismantle the whole unit, take out the evaporator and really clean the whole damn thing, and depending on the skill of the technician, this can reach 90% effectiveness or more. But better to get someone who knows your model to do it.
Just a disclaimer, the percentages shown in this article is by guessing, I'm not an expert in aircon but I do know general servicing is bullshit since I opened it up and saw for myself, what a terrible waste of my money.